Epoxy resins are one of the important classes of polymeric resins used in various fields of applications such as electrical industries, adhesives, coating, as well as composite material with various reinforcing materials such as carbon fibres, Aramide, Kevlar, polyesters and fibre glass and as concrete polymer additives.
Most of the epoxy resins are from petrochemical resources, the non-renewable resources with growing costs. The epoxy resin industry generates considerable pollution since more than 60% of the epoxy resins consumed require organic solvents and diluents such as xylenes, toluene, petroleum ethers, oils and volatile organic compounds (VOC).
Several types of additives and activators are used with epoxy resins such as phenols and tertiary amines as curing activators. The polluting nature of phenols and tertiary amines is well established due to their extremely high reactivity and volatility. Accordingly, most current European standards require phenol free and zero volatile organic content (VOC) for industrial products.
Lignin is an aromatic polyphenol that is a naturally occurring renewable product. Lignin can be obtained as a waste by-product of the paper industry. Millions of tonnes are produced industrially at a significant environmental and economic cost to the industry. Currently, lignin waste must be transformed from black liquor to semi-solid waste (about 85% lignin) and then dumped or burned, all at significant cost (economically and environmentally).
Lignin represents 15-35% of wood, and accordingly is the most abundant renewable organic material on the earth. Pulping industries separate cellulose from the wood composition leaving lignin and hemicelluloses as waste by-products known as black liquor. In the sulphite process pulp industries the main by-product is lignosulphonate. The global annual production capacity is about 1.8-2.0 million tons. Each ton of pulping products produces 330-540 kg of lignosulphonate. Most of the lignosulphonate (66%) produced in pulping industries is burned (resulting in significant SO2 pollution) and 34% is treated and dumped which is costly.
Therefore, there is a need to develop water based lignins that do not have the economic or environmental costs associated with the prior use and handling of lignins. The embodiments provided herein satisfy this need as well as others.